摘要:

AbstractMany strains of a pathogenic fungus were isolated from diseased sunflower leaf tissue. According to their characteristics they belonged to the genusSeptoria. Leaf speck symptoms, characteristic for spontaneous infection, were also reproduced by artificial inoculation of sunflower plants in the greenhouse.Comparing the morphological, cultural and pathogenic properties of the isolated fungus with other sunflower pathogens, it was indicated that the strains, originating from diseased sunflower leaves represented a new, so far not described species. Therefore, for the causal agent of this disease, the nameSeptoria helianthinaPetrov&Arsenijevic was suggested.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00304.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThirty‐four isolates ofVerticillium dahliaeKleb. from nine different genera of dicotyledonous host plants and a broad range of geographic regions were analysed genotypically, Random amplified polymorphic DNA (RAPD) markers were used for the estimation of the genetic variability within the species. Using four primers for the analysis, 79 distinct fragments were obtained. The derived phenogram clustered the isolates in two main groups; one consisted almost entirely ofV. dahliaeisolates from oilseed rape (Brassica napus napus), the other group comprised isolates from a wide range of host plants. No correlation between geographic location of the isolates and the RAPD‐pattern was observed.Sequencing of the gene for the 18SrRNA and calculation of the phylogenetic tree integrated the deuteromycetous fungusV. dahliaeinto the sexual system of the filamentous ascomyce

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00305.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe efficiency by which tomato spotted wilt virus (TSWV) was transmitted to plants and leaf disks by the vectorFrankliniella occidentalis, was analysed. The virus was efficiently transmitted toDatura stramonium, Impatienssp. and tobacco plants, i.e. 60–100% of the plants became infected when 1–3 viruliferous thrips were confined per plant for a period of 3 days. However, lettuceexhibited a lower susceptibility since only 25% of the test plants were infected when challenged by 10 viruliferous thrips per plant for 3 days. In contrast, complete resistance was found when transgenic tobacco plants, expressing the nucleocapsid protein of TSWV, were challenged with up to 10 viruliferous thrips per plant, whereas all non‐transgenic control plants were infected when 5 viruliferous thrips per plant were used. To improve and accelerate the tramission studies, the applicability of leaf disks in these studies was tested. Leaf disks of 16 different plant species appeared to be highly susceptible. Infection ratings ranging from 51.6 to 95.0% were obtained when one viruliferous adult was placed singly on these leaf disks for a period for 24 h. The leaf disk assay was also employed to screen resistance of transgenic plants expressing the nucleocapsid protein of TSWV. One transgenic tomato line displayed complete immunity whereas a second line appeared to be susceptible. For the transgenic tobacco line, positive ELISA reactions were found for a few leaf disks (7.5%) suggesting that some virus replication did occur. However, the ELISA readings for these disks were significantly lower than those for leaf disks of non‐transgenic controls. Finally, the significance of the use of the leaf disks and test plants in virus‐vector studies is

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00306.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe polymerase chain reaction (PCR) was used to amplify the ITS2 region of nuclear ribosomal DNA from sixPhytophthoraspecies which comprise taxonomic Group IV. Digestion of the ca. 600 bp PCR product with restriction enzymesAluI,DraI,HhaI,HinfI,MspI, andTaqI revealed variation which allowed relationships among the species to be assessed. P.infestans, P.mirabilisand P.phaseoliwere indistinguishable from one another with all enzymes tested. WithAluI andTaqI.P. ilicis,P. colocasiae. andP. hibernaliseach showed unique banding patterns different from the common banding pattern shared byP. infestans.P. mirabilis. andP. hibernalis.DraI allowed differentiation ofP. ilicisandP. colocasiaefromP. infestans,P. mirabilis,P. phaseoli, andP. hibernalis. all of which shared a common banding pattern.HhaI allowed differentiation ofP. colocasiaeandP. hibernalisfromP. infestans, P. mirabilis, P. phaseoli, andP. ilicis.HinfI allowed differentiation ofP. ilicisandP. hibernalis, (each of which showed a unique banding pattern) fromP. infestans, P. mirabilis, P. phaseoli, andP. colocasiae.MspI allowed differentiation ofP. hibernalisfrom the other five species. Species groupings determined by restriction analysis of ITS2 were consistent with those based on morphological criteria. These results show that restriction analysis of PCR‐amplified TS2 regions can be useful as an adjunct to morphological criteria inPhytophthoraspecies identificatio

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00307.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractHigh molecular weight DNA ofPhytophthora infestanswas extracted using a modification of the commercial QIAGEN column procedure. Both a ‘maxi’ and ‘mini’ procedure are described. The maxi procedure utilizes a QIAGEN‐tip 500 column while the mini procedure utilizes a QIAGEN‐tip 20 column. When fungal protoplasts were used as starting material from 9 g (fresh weight) of mycelium, nearly 500 μg of DNA in the size range of 20–200 kb was obtained and the product was successfully used in construction of a lambda genomic library. The modified QIAGBN method can replace the more timeconsuming, and expensive cesium chloride density gradient centrifugation for extraction of ultra‐pure DNA

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00308.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe Weibull model is a flexible growth model that describes both general population growth and plant disease progress. However, lack of an asymptotic parameter has limited its wider application. In the present study, an asymptotic parameter K was introduced into the original Weibull model, written as;y=K{1 − exp [− (t−a)c]}, in whicha,b,candKare location, scale, shape, and asymptotic parameters, respectively, y is the proportion of disease and t is time. A wide range of simulated disease progress data sets were generated using logistic, Gompertz and monomolecular models by specifying different parameter values, and fitted to both original and modified Weibull models. The modified model provided statistically better fits for all data than the original model. The modified model can thus improve the curve‐fitting ability of the original model which often failed to converge, especially when the asymptote is less than 1.0. Actual disease progress data on wheat leaf rust and tomato root rot with different asymptotic values were also used to compare the original and modified Weibull models. The modified model provided a statistically better fit than the original model, and model estimates of asymptotic parameter K were nearly identical to the actual disease maxima reflecting the characteristics of the host‐pathosystem. Comparison of logistic, Gompertz, and Weibull models including parameter K by fitting to the observed data on wheat leaf rust and tomato root rot revealed the applicability of the modified Weibull model, which in a majority of cases provided a statistically sup

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00309.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractAn isolate of BYDV (BYDV‐OC), from barley in Northwest Italy with typical symptoms of yellowing and dwarfing, was transmitted byRhopalosiphum padi, Sitobion fragariae. S. avenae, Metopolophium festucae, R. maidisandM. dirhodum, but not byMyzus persicaeorSchizaphis graminum. It reacted in DAS‐ELISA with monoclonal and polyclonal antisera to PAV, but not with antibodies to MAV, RPV and RMV. A polyclonal antiserum prepared to BYDV‐OC did not react with MAV‐like, RPV‐like, or RMV‐like isolates of BYDV in ELISA or in Western blots. The concentration of BYDVOC inAvena byzantinaplants decreased from weeks 1 to 10 after inoculation, but the total virus content per plant increased up to weeks 7 to 8, following the increase of p

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00310.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractStudies were conducted in eastern Kenya to determine the common legume crop and weed hosts ofMacrophomina phaseolina(Tassi) Goid., the inciter of charcoal rot disease. The effect of maize, sorghum, bean, and cowpea on the soil inoculum level was also investigated after field inoculation. All the legume crops and weeds tested were found to be infected by the pathogen after artificial inoculation. Common bean, soybean, cowpea were the most susceptible while pigeonpea, green gram, and hyacinth bean were moderately susceptible. Groundnut, chickpea.Cassiaspp. andCrotalariaspp. were least susceptible after artificial inoculation, Monocropping of sorghum, maize, cowpea and common bean for three consecutive crop seasons increasedM. Phaseolinasoil inoculum in ascending order.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00311.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractPolymerase chain reaction (PCR) amplification was carried out with a primer pair targeting a sequence in the genome ofXanthomonas campestrispv.pelargonii, the causative agent of bacterial blight in geraniums. PCR amplification with the primer pair XcpMl/XcpM2 using total nucleic acid preparations from 22 geographicallydiverse isolates ofX. campestrispv.pelargoniigenerated a major 197 bp DNA product. In contrast, no major amplification products were consistently generated from 12 other pathovars ofX. campestrisor from 19 isolates representing 10 different plant pathogenic bacteria, including two other bacterial pathogens of geraniums,Corynebacterium fasciansandPseudomonas cichorii. After PCR using this primer pair, between 1380 and 13800 copies of theX, campestrispv.pelargoniibacterial DNA target as template were detected by ethidium bromide staining of agarose gels, and between 13.8 and 138 copies by blot hybridization to a pathovar‐specific biotinylated probe. Similarly, between 630 and 6300 colonyforming units (CFU) of X.campestrispv.pelargoniicould be detected after ethidium bromide staining of agarose gels, and between 63 and 630 CFU after blot hybridization. The PCR‐based assay was used to identifyX. campestrispv.pelargoniiin diseased geraniums; whereas discrete amplification products were not obtained with healthy pla

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00312.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractHeterobasidion annosum, the casual agent of root and butt rots of trees is one of the most important plant pathogens in temperate coniferous regions of the world. It is comprised of several intersterility groups with different host preferences. Of the H. annosum isolates from various geographical regions belonging to various intersterility groups, 36 showed group‐specific banding patterns in RAPD assay. More polymorphisms were found within the S‐ and F‐group isolates than in the P group. Genetic similarities among the isolates were determined by UPGMA clustering revealing the presence of four major clusters: P, S, F, and the North American S. The P group was the most distinctive of all the other groups, while the European S and F and the North American S were more closely related. The P group showed only 20% similarity to the other groups and may be referred to as a subspecies. The North American S group was separate from the European S group. The potential influence of the historical spread of coniferous trees in the isolate genetic differentiation in Europe is disc

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1996.tb00313.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY